Tobacco composition and smoking unit



United States Patent Walter Linwood Haden, .lru, Metuchen, NJ, assignor to Minerals & Chemicals Philipp Corporation, a corporation of Maryland No Drawing. Filed Nov. 14, 1957, Ser. No. 696,314

9 Claims. (Cl. 13117) This invention relates to smoking compositions and to smokable articles including a novel class of inorganic material intimately associated with tobacco whereby the pyrogenesis of deleterious high-molecular weight substances normally encountered during the burning of tobacco particles is substantially reduced.

There exists strong clinical, statistical and pathological evidence that certain constituents of tobacco smoke condensate are potentially carcinogenic when deposited on human tissue. These carcinogens have been reported to be mixtures of essentially neutral high-molecular weight polycyclic aromatic hydrocarbons, the carcinogenic potency of any mixture depending on the species present. Several general types of polycyclic aromatic hydrocarbons are present in a carcinogenic fraction of such smoke condensate, or tar, and undoubtedly many individual molecular species are hence present. In general, known carcinogens contain at least four condensed benzene rings per molecule and may include derivatives and substitution products of benzanthracene, phenanthrene, pyrene, chrysene and other types of condensed-ring aromatic hydrocarbons. Certain of these highly carcinogenic compounds such as 1,2,5,6-dibenzanthracene and deriva tives of 3,4benzpyrene have been identified, whereas others are as yet unidentified or have not been resolved into individual molecular species. Such deleterious polycyclic hydrocarbons are undoubtedly of pyrogenic origin since they cannot be isolated from raw tobacco prior to the pyrolysis thereof.

Such noxious substances are ordinarily carried as dispersed droplets or solid particles in the effluent smoke stream and thence into the smokers respiratory system along with the aroma and taste producing constituents of the smoke. Aside from their alleged pathological effect it appears that certain constituents of tars are in part responsible for a sharp, irritating taste imparted to smoke from a cigarette or the like.

There is strong indication that the generation of these allegedly carcinogenic compounds is favored by high temperatures, whereby they are present in greater quantity in the tars from a cigarette than in the tars from a cigar or pipe, which when smoked develop peak temperatures several hundred degrees lower than that of a cigarette. At the peak temperature of about 880 C. :35 C. developed in a conventional cigarette when puffed such carcinogens are generated in potentially dangerous quantities. There is good evidence that the lowering of this peak to 800 C. or less results in decreased generation of the potentially carcinogenic substances with substantial benefits accruing from lowering the burning temperature to about 720 C. or less.

Accordingly, it is a principal object of the instant invention to provide a tobacco composition including a novel treating solid which functions to substantially reduce the concentration in the smoke effluent from the mixture those deleterious high-molecular weight compounds, particularly polycyclic aromatic compounds, pyrogenetically or otherwise produced.

It is another object of the invention to incorporate a novel treating solid in smoking tobacco to permit the pyrolysis of said tobacco to take place to a lower tem- 3,126,011 Patented Mar. 24, 1964 I perature than would be encountered in the absence of said treating solid.

Another object of the invention is the provision of a composition including tobacco intimately associated with a novel inorganic treating agent capable of lowering the burning temperature of the tobacco.

It is another object of the invention to provide smoking units including such compositions which inherently possess the ability to simultaneously improve the aroma of the smoke from the tobacco and substantially prevent the generation of deleterious high-molecular weight polycyclic compounds.

Other objects will be apparent from an inspection of the following description of the invention.

The instant invention is the result of my discovery that the presence in smoking tobacco of certain inoxious incombustible solids capable of melting endothermically at a temperature at or below the burning temperature of the tobacco results in an improved smoking composition. The term innoxious as used herein refers not only to the quality of being noninjurious to health but also to the quality of being inoffensive to the senses. Although solids which melt endothermically at temperatures as low as about 300 C. may be used in the practice of the invention with some "benefit, nevertheless the melting of such a material will occur a distance from the advance of the flame-front and greater dissipation of the heat loss will occur than when the material employed undergoes endothermic melting at or within about C. of the flamefront temperature. The theoretically ideal material for the purposes of the instant invention is one which melts at the temperature of the flame-front for the particular tobacco-solid mix. In general, materials melting endothermically from about 450 C. up to about the normal burning temperature of the particular tobacco in the absence of an added solid are particularly satisfactory for the purpose of my invention.

Suitable solids for the purpose of my invention include innoxious solids melting endothermically without evolution of noxious volatiles and being non-explosive and nonoxidizing at the combustion temperature of the tobaccosolid mixture, the melting point of the pure solid being between about 4501000 C. and particularly from about 450 to 880 C. :30" C. Preferred solids are borates, phosphates, silicates, and hydrates thereof with cations selected from potassium, lithium, and sodium. Species include sodium tetraborate, soodium pyrophosphate, sodium disilicate, lithium metaborate, lithium silicate, lithium orthophosphate, potassium carbonate, potassium metaphosphate, and hydrates thereof. Also suitable are sodium molybdate, sodium pyrovanadate, boron oxide or hydrates thereof. When the composition of the ash constituents originating in the tobacco or treating agents is such that additives normally melting above 880 :30 C. form lower melting mixtures, salts normally melting above the preferred range, suitable up to about 1000" C. may be used. For this reason potassium metaborate and potassium silicate, sodium pyrophosphate, will generally be beneficially incorporated in the tobacco although they melt within the range of from about 880 1000" C.

Nitrates and chlorates melting within the expressed temperature ranges are unsatisfactory because of their oxidizing nature and tendency to promote explosive combustion. Chlorides as well as sulfates are unsatisfactory because of possible evolution of noxious gases.

It will be understood that the invention in its broadest aspect is not restricted to any specific quantity or range of quantities of salt additives. The optimum quantity is that which lowers the burning temperature of the tobacco mineral mixture to about 800 C. or more preferably to 720 C., or lower. In general from about 1 to 20%, and particularly from about 3 to 10%, based on the weight of tobacco, produces outstanding benefits. The specific amount of any particular meltable additive needed to reduce the burning temperature to a predetermined level will vary with the type of tobacco and the moisture content in the mixture. Other factors to be considered in determining the ratio of solid to tobacco include ability of the mixture to sustain burning, analysis of combustion product distribution, and taste and aroma of the eifluent smoke.

The solid is preferably incorporated in the smoking unit in finely divided form, usually less than about microns and preferably having a substantial portion between about 0.5 and 2.0 microns. in general the more highly subdivided the solid the greater the adhesion to the tobacco. It has been found that coarser particles, for example 44 micron particles, are more prone than more finely-divided particles to pass into the smokers mouth. Of course the particular range of particle size used in a tobaccosolid mix will depend on such factors as moisture content, presence of tacky humectants, presence of an agent to bind the mineral to the tobacco surface, mode of application to the tobacco, size of tobacco particles, presence of and nature of filter-tip in the smoking unit, quantity of solid used and locus of solid placement.

A filter, either of the well-known type which is integral with the smoking unit or of the holder type including a filter, is preferably employed in a smoking unit when tobacco is treated by the process herein taught. The filter may be fibrous and/ or include absorbents such as silica, clay or the like. The purpose of the filter is to prevent any inspiration of finely-divided particles which may occur if the smoking unit is subjected to dry warm weather for prolonged periods. The filter imposes a bed of material capable of entraining the particle which might otherwise be drawn into the smokers mouth. However, by proper selection of moisture content and, in some cases, inclusion of about 2 to 4% (based on the weight of the tobacco) of humectant or by otherwise bonding the minerals to the tobacco surface the filter may be omitted.

Although the description of the invention has been made with particular reference to cigarettes, it will be understood that the practice as herein taught is applicable to any smoking unit.

The following examples are given only for the sake of further illustrating the invention and are not to be construed as limiting the scope thereof.

Example I A cigarette of the present invention is prepared by admixing 1.0 gram of pre-humected cigarette tobacco (a blend adapted to burn at a peak temperature of about 880 C.) with 0.05 gram of pulverized sodium metaphosphate and packing the tobacco mix into a cylindrical cigarette-paper having a fibrous filter-tip.

Example 11 0.04 gram of the potassium pentaborate is intermingled with 1.0 gram of cigarette tobacco and the mixture is made into a cigarette as in Example I.

Example III A dilute aqueous solution of sodium metaborate is sprayed on shredded blended tobacco in amount sufficient to leave a residue of 0.05 gram of the salt (calculated as NaBO resident on each 1.0 gram of tobacco (moisturefree basis).

Furthermore, the invention is not restricted to any method of commingling the tobacco and solid, any suitable means for intimately associating the components being satisfactory. For example, when the salt is water-insoluble or substantially water-insoluble a slurry of salt particles may be added to leaf or particulated tobacco, suitably by spraying a slurry of the mineral particles onto the tobacco. Water-soluble salts may be dissolved prior to spraying onto the tobacco. Likewise, a salt, watersoluble or water-insoluble, can be incorporated into socalled homogenized leaf tobacco by forming comrninuted tobacco and salt into a coherent sheet-like mass with the aid of a suitable binder.

Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A smoking mixture consisting essentially of tobacco shreds having mixed therewith from 3% to 10% by weight of finely-divided solid particles of an alkali metal salt of an acid selected from the group consisting of silicates, phosphates and borates, and which has a melting point within the range of 450 C. to 1000 C., said tobacco shreds consisting essentially of naturally occurring tobacco.

2. A smoking mixture comprising essentially tobacco shreds having uniformly mixed therewith from 3% to 10% by weight of finely-divided solid particles of sodium metaphosphate as the sole phosphate additive.

3. A smoking mixture comprising essentially tobacco shreds having uniformly mixed therewith from 3% to 10% by weight of finely-divided solid particles of potassium pentaborate.

4. A smoking mixture comprising essentially tobacco shreds having uniformly mixed therewith from 3% to 10% by Weight of finely-divided solid particles of sodium metaborate.

5. A cigarette consisting essentially of shreds of tobacco having incolporated therewith from 3% to 10% by weight of finely-divided solid particles of an alkali-metal salt of an acid selected from the group consisting of silicates, phosphates and borates and which has a melting point within the range of 450 C. to 1000 C., said tobacco shreds consisting essentially of naturally occurring tobacco.

6. The cigarette of claim 5 in which said salt is sodium metaphosphate.

7. The cigarette of claim 5 in which said salt is potassium pentaborate.

8. The cigarette of claim 5 in which said salt is sodium metaborate.

9. A smoking tobacco mixture comprising tobacco and about 1 percent to about 10 percent by weight of the tobacco of boric oxide, said boric oxide serving to lower the maximum burning temperature of the tobacco.

References Cited in the file of this patent UNITED STATES PATENTS 467,055 Schneider Jan. 12, 1892 604,338 Rickard et a1 May 17, 1898 1,996,002 Seaman Mar. 26, 1935 2,029,494 Loewenthal Feb. 4, 1936 2,108,860 Kaufi'man Feb. 22, 1938 2,329,927 Morton Sept. 21, 1943 2,613,673 Sartoretto et al. Oct. 14, 1952 2,776,916 Ericcson Jan. 8, 1957 2,786,471 Graybeal Mar. 26, 1957 2,808,057 Jaksch Oct. 1, 1957 2,839,065 Milton June 17, 1958 2,914,072 Tyrer Nov. 24, 1959 FOREIGN PATENTS 671,126 Germany Jan. 31, 1939 869,465 Germany Nov. 12, 1953 OTHER REFERENCES Making Cigarettes Safe, from Time, Apr. 22, 1957 (p UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,126,011 March 24, 1964 Walter Linwood Haden, Jr.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 47, for "soodium pyrophosphate" read sodium pyrophosphate line 49, for "potassium carbonate" read potassium pentaborate column 2, line 54,

for "above 8803 30 C, read above 880-1530 Co Signed and sealed this 14th day of July 1964,

(SEAL) Attest:

ESTON G. JOHNSON EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A SMOKING MIXTURE CONSISTING ESSENTIALLY OF TOBACCO SHREDS HAING MIXED THEREWITH FROM 3% TO 10% BY WEIGHT OF FINELY-DIVIDED SOLID PARTICLES OF AN ALKALI METAL SALT OF AN ACID SELECTED FROM THE GROUP CONSISTING OF SILICATES, PHOSPHATES AND BORATES, AND WHICH HAS A MELTING POINT WITHIN THE RANGE OF 450*C. TO 1000*C., SAID TOBACCO SHREDS CONSISTING ESSENTIALLY OF NATURALLY OCCURRING TOBACO. 